[PROBLEM] To recover phosphorus accumulated in a sewage-treatment plant or the like at a low cost in such a manner as to facilitate the utilization of the thus recovered phosphorus. To efficiently utilize the recovered phosphorus as a fertilizer. [SOLUTION] Phosphorus in waste water, which is a phosphorus source, is adsorbed by a phosphorus recovery material formed of an amorphous calcium silicate-based material and thus recovered. After adding the phosphorus recovery material to the waste water that is a phosphorus source, it is preferred to adjust the pH value of the waste water to 7.0 or higher. Also, it is preferred that the waste water that is a phosphorus source is decarbonated by reducing the pH value thereof to 6.0 or lower and then the phosphorus recovery material is added. As the phosphorus recovery material, an aggregate of an amorphous calcium silicate hydrate and Ca(OH) 2 and having a Ca/Si molar ratio of 0.8-20 inclusive is preferred. The aggregate may be obtained by solid-liquid separation and drying. Alternatively, a slurry or paste containing the aggregate may be used. The recovered phosphorus recovery material can be used as a fertilizer.